/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.http.server.reactive;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.charset.Charset;
import java.security.cert.X509Certificate;
import java.util.Enumeration;
import java.util.Map;
import javax.servlet.AsyncContext;
import javax.servlet.AsyncEvent;
import javax.servlet.AsyncListener;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.Cookie;
import javax.servlet.http.HttpServletRequest;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import reactor.core.publisher.Flux;

import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.http.HttpCookie;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.LinkedCaseInsensitiveMap;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.util.StringUtils;

/**
 * Adapt {@link ServerHttpRequest} to the Servlet {@link HttpServletRequest}.
 *
 * @author Rossen Stoyanchev
 * @since 5.0
 */
class ServletServerHttpRequest extends AbstractServerHttpRequest {

    private static final String X509_CERTIFICATE_ATTRIBUTE = "javax.servlet.request.X509Certificate";

    private static final String SSL_SESSION_ID_ATTRIBUTE = "javax.servlet.request.ssl_session_id";


    protected final Log logger = LogFactory.getLog(getClass());


    private final HttpServletRequest request;

    private final RequestBodyPublisher bodyPublisher;

    private final Object cookieLock = new Object();

    private final DataBufferFactory bufferFactory;

    private final byte[] buffer;


    public ServletServerHttpRequest(HttpServletRequest request, AsyncContext asyncContext,
                                    String servletPath, DataBufferFactory bufferFactory, int bufferSize) throws IOException {

        super(initUri(request), request.getContextPath() + servletPath, initHeaders(request));

        Assert.notNull(bufferFactory, "'bufferFactory' must not be null");
        Assert.isTrue(bufferSize > 0, "'bufferSize' must be higher than 0");

        this.request = request;
        this.bufferFactory = bufferFactory;
        this.buffer = new byte[bufferSize];

        asyncContext.addListener(new RequestAsyncListener());

        // Tomcat expects ReadListener registration on initial thread
        ServletInputStream inputStream = request.getInputStream();
        this.bodyPublisher = new RequestBodyPublisher(inputStream);
        this.bodyPublisher.registerReadListener();
    }

    private static URI initUri(HttpServletRequest request) {
        Assert.notNull(request, "'request' must not be null");
        try {
            StringBuffer url = request.getRequestURL();
            String query = request.getQueryString();
            if (StringUtils.hasText(query)) {
                url.append('?').append(query);
            }
            return new URI(url.toString());
        } catch (URISyntaxException ex) {
            throw new IllegalStateException("Could not get URI: " + ex.getMessage(), ex);
        }
    }

    private static HttpHeaders initHeaders(HttpServletRequest request) {
        HttpHeaders headers = new HttpHeaders();
        for (Enumeration<?> names = request.getHeaderNames();
             names.hasMoreElements(); ) {
            String name = (String) names.nextElement();
            for (Enumeration<?> values = request.getHeaders(name);
                 values.hasMoreElements(); ) {
                headers.add(name, (String) values.nextElement());
            }
        }
        MediaType contentType = headers.getContentType();
        if (contentType == null) {
            String requestContentType = request.getContentType();
            if (StringUtils.hasLength(requestContentType)) {
                contentType = MediaType.parseMediaType(requestContentType);
                headers.setContentType(contentType);
            }
        }
        if (contentType != null && contentType.getCharset() == null) {
            String encoding = request.getCharacterEncoding();
            if (StringUtils.hasLength(encoding)) {
                Charset charset = Charset.forName(encoding);
                Map<String, String> params = new LinkedCaseInsensitiveMap<>();
                params.putAll(contentType.getParameters());
                params.put("charset", charset.toString());
                headers.setContentType(
                        new MediaType(contentType.getType(), contentType.getSubtype(),
                                params));
            }
        }
        if (headers.getContentLength() == -1) {
            int contentLength = request.getContentLength();
            if (contentLength != -1) {
                headers.setContentLength(contentLength);
            }
        }
        return headers;
    }


    @Override
    public String getMethodValue() {
        return this.request.getMethod();
    }

    @Override
    protected MultiValueMap<String, HttpCookie> initCookies() {
        MultiValueMap<String, HttpCookie> httpCookies = new LinkedMultiValueMap<>();
        Cookie[] cookies;
        synchronized (this.cookieLock) {
            cookies = this.request.getCookies();
        }
        if (cookies != null) {
            for (Cookie cookie : cookies) {
                String name = cookie.getName();
                HttpCookie httpCookie = new HttpCookie(name, cookie.getValue());
                httpCookies.add(name, httpCookie);
            }
        }
        return httpCookies;
    }

    @Override
    public InetSocketAddress getRemoteAddress() {
        return new InetSocketAddress(this.request.getRemoteHost(), this.request.getRemotePort());
    }

    @Nullable
    protected SslInfo initSslInfo() {
        if (!this.request.isSecure()) {
            return null;
        }
        return new DefaultSslInfo(
                (String) request.getAttribute(SSL_SESSION_ID_ATTRIBUTE),
                (X509Certificate[]) request.getAttribute(X509_CERTIFICATE_ATTRIBUTE));
    }

    @Override
    public Flux<DataBuffer> getBody() {
        return Flux.from(this.bodyPublisher);
    }

    /**
     * Read from the request body InputStream and return a DataBuffer.
     * Invoked only when {@link ServletInputStream#isReady()} returns "true".
     */
    @Nullable
    protected DataBuffer readFromInputStream() throws IOException {
        int read = this.request.getInputStream().read(this.buffer);
        if (logger.isTraceEnabled()) {
            logger.trace("InputStream read returned " + read + (read != -1 ? " bytes" : ""));
        }

        if (read > 0) {
            DataBuffer dataBuffer = this.bufferFactory.allocateBuffer(read);
            dataBuffer.write(this.buffer, 0, read);
            return dataBuffer;
        }

        return null;
    }

    @SuppressWarnings("unchecked")
    @Override
    public <T> T getNativeRequest() {
        return (T) this.request;
    }


    private final class RequestAsyncListener implements AsyncListener {

        @Override
        public void onStartAsync(AsyncEvent event) {
        }

        @Override
        public void onTimeout(AsyncEvent event) {
            Throwable ex = event.getThrowable();
            ex = ex != null ? ex : new IllegalStateException("Async operation timeout.");
            bodyPublisher.onError(ex);
        }

        @Override
        public void onError(AsyncEvent event) {
            bodyPublisher.onError(event.getThrowable());
        }

        @Override
        public void onComplete(AsyncEvent event) {
            bodyPublisher.onAllDataRead();
        }
    }


    private class RequestBodyPublisher extends AbstractListenerReadPublisher<DataBuffer> {

        private final ServletInputStream inputStream;

        public RequestBodyPublisher(ServletInputStream inputStream) {
            this.inputStream = inputStream;
        }

        public void registerReadListener() throws IOException {
            this.inputStream.setReadListener(new RequestBodyPublisherReadListener());
        }

        @Override
        protected void checkOnDataAvailable() {
            if (!this.inputStream.isFinished() && this.inputStream.isReady()) {
                onDataAvailable();
            }
        }

        @Override
        @Nullable
        protected DataBuffer read() throws IOException {
            if (this.inputStream.isReady()) {
                return readFromInputStream();
            }
            return null;
        }

        @Override
        protected void readingPaused() {
            // no-op
        }


        private class RequestBodyPublisherReadListener implements ReadListener {

            @Override
            public void onDataAvailable() throws IOException {
                RequestBodyPublisher.this.onDataAvailable();
            }

            @Override
            public void onAllDataRead() throws IOException {
                RequestBodyPublisher.this.onAllDataRead();
            }

            @Override
            public void onError(Throwable throwable) {
                RequestBodyPublisher.this.onError(throwable);

            }
        }
    }

}
